Embodiments of the invention can be directed to systems and methods that utilize capillaries to analyze samples. For example, some embodiments of the invention relate to systems and methods for accurately determining serum indices, e.g. for lipemia, hemolysis, and icterus, from serum and plasma samples in uncapped sample tubes.
Laky or chylous samples, of lipemic, hemolytic or icteric patients commonly interfere with other laboratory tests that use optical methods. Thus, for reliable sample handling automation, it is desirable to measure serum index before a sample is committed to an analyzer for testing to avoid erroneous measurements. The serum index is typically measured by sample aspiration and measurement on an analyzer instrument. For serum index to be viable in an automation device, the complete cycle time for a sample needs to match or exceed the speed of the sample throughput.
U.S. Pat. No. 5,734,468 (US '468) discloses a method and device for detecting the presence of hemolysis, icteris and lipemia in a serum sample aspirated in a transparent aspiration probe connected to a pump (see FIG. 4 of US '468). In the disclosed system, a liquid sample volume from a sample container is aspirated into the aspiration probe by applying an aspiration vacuum. The fluid sample is aspirated until the filling level in the aspiration probe reaches an optical measurement section (see FIG. 2 of US '468). At the optical measurement section, a connected fiber optics emits light into the optical transparent section and detects the transmitted part of light in a detection fiber optics at the opposite side.
A disadvantage of the disclosed system of US '468 is the need to include a washing step for the aspiration probe including the measurement section, before a subsequent sample can be measured. This reduces the throughput of the system and increases the risk of erroneous measurement results due to contamination of the subsequent sample.
U.S. Pat. No. 7,688,448 B2 (US 448) discloses an apparatus that is used to measure the serum index by a non-contact approach, emitting light through the primary sample container (see schematics in FIG. 4 of US '448). The emitted light spectra of two different light sources are combined by a beam splitter element and the combination is directed to one defined point of the primary sample container. The absorption signal is detected with a detector optic on the opposite side of the container and is recorded in a computer unit (see FIG. 18 of US '448).
A disadvantage of the disclosed apparatus of US '448 is that in the automatic processing of primary sample containers in an laboratory environment, labels may be attached to the containers. Labels can disturb or suppress the signal from the emitting optics. This makes the apparatus unable to detect a valid serum index result for a sample provided within a primary sample container.
To overcome the previously described disadvantage of measuring through a label applied to a primary sample container, US 2010/0303331 A1 (US '331) suggests using uncapped sample containers in combination with a sensor optic in a light tight measurement container. The disclosed apparatus in US '331 uses a light source below the sample container position and a camera in a moveable light tight box. When a sample is provided by a conveyor track at the measurement position, the box is lowered until it produces a light tight enclosure with the conveyor track (see FIG. 5B of US '331). The light source then emits a broad spectrum of light from below to the sample and the camera detects the transmitted signal from the sample to determine the serum index result.
A disadvantage of the disclosed apparatus in US '331 is that for previously centrifuged samples, no valid signal for serum index can be measured, since the emitted light will be almost completely blocked by the coagulum. Thus, this system is unsuitable for determining valid serum index results, based on blood serum or plasma.
Embodiments of the invention address these and other problems, individually and collectively.